In some countries, neutral admittance protection has become a common earth fault protection function. It has been reported to provide improved effectiveness in earth fault detection when compared to the traditional residual current based earth fault protection in unearthed and compensated distribution networks. J. Lorenc et. al, Admittance Criteria For Earth Fault Detection In Substation Automation Systems in Polish Distribution Power Networks, CIRED 97, Birmingham, June 1997, discloses examples of the implementation of the neutral admittance based earth fault protection.
The admittance-based earth fault protection can be based on evaluating the quotient between fundamental frequency phasors of residual current Īo and residual voltage Ūo: Yo=Īo/−Ūo 
Alternatively, the admittance calculation can be made by utilizing so-called delta quantities, i.e. the change in residual quantities due to the earth fault: Yo=(Īo—fault−Īo—prefault)/−(Ūo—fault−Ūo—prefault)where “fault” denotes the time during the fault and “prefault” denotes the time before the fault.
The result can then be compared with operating boundaries on an admittance plane. The admittance protection, similar to other earth fault protection functions, can use a Uo overvoltage condition as a common criterion for the initial fault detection. The setting value for Uo start can be set above the maximum healthy Uo level of the network in order to avoid false starts.
The admittance protection can provide many attractive features such as inherent immunity to fault resistance, generally universal applicability, good sensitivity and easy setting principles. However, in some cases, the sensitivity of the admittance protection might not be good enough.
In Jozef Lorenc et al., Detection of the Intermittent Earth Faults in Compensated MV Network, 2003 IEEE Bologna Power Tech Conference, an admittance criterion utilizing wavelets is proposed. A drawback related to this solution, however, is that it is dedicated on intermittent earth faults and as such it is not applicable to permanent earth faults.